错把疯狗当朋友
[cuò bă fēng gŏu dāng péng yŏu]
'错把疯狗当朋友' can be translated to mean making the mistake (错cuò means 'wrong') of treating a crazy dog (metaphorically someone untrustworthy) as a friend. This implies someone got betrayed or let down by a trusted one who proved unworthy of such trust.